An autonomous drug delivery system advantageously utilizes physiological monitor outputs so as to automatically give a bolus of a rescue drug or other necessary medication when certain criteria and confidence levels are met. An emergency button is provided to manually trigger administration of the rescue drug. The rescue drug may be an opioid antagonist in response to an analgesia overdose, a hypotensive drug to avert an excessive drop in blood pressure or an anti-arrhythmia drug to suppress abnormal heartbeats, to name a few.